In general, an oil pan apparatus of the above type is fastened to the underside of a lubrication target mechanism, and is configured so as to store oil in the internal space of an oil pan cover, which constitutes an outer cover for the oil pan apparatus. An oil-pan-attached machine (e.g., engine or automatic transmission device), which is equipped with the oil pan apparatus, is configured so that an oil pump takes in the oil from an oil intake port of an oil strainer, which is positioned in the oil pan apparatus, and supplies the oil to lubrication target members (e.g., gear, camshaft, cylinder, and piston) in the lubrication target mechanism. Further, the oil-pan-attached machine is configured so that the oil, which is supplied to the lubrication target members as described above, lubricates the lubrication target members, absorbs heat, which is generated due, for instance, to friction, and flows back to the oil pan apparatus from the lubrication target mechanism by gravitation.
A two-tank oil pan structure, which is disclosed, for instance, by Patent Reference 1, is widely known as a conventional oil pan structure.
[Patent Reference 1] Japanese Patent JP-A No. 278519/2003
In an oil pan apparatus having the two-tank oil pan structure which is disclosed by Patent Reference 1 (hereinafter referred to as the conventional technology), a partition plate is positioned within the internal space of an outer board that corresponds to the oil pan cover. The partition plate divides the internal space into two sections: a first chamber in which the oil strainer is located, and a second chamber which is adjacent to the first chamber.
The partition plate is provided with communication paths that permit the interchange of oil between the first and second chambers. Each communication path is provided with an open/close valve for permitting the passage of oil in the communication path in accordance with the oil temperature. In other words, the open/close valve is configured so as to control the interchange of oil through the communication paths between the first and second chambers in accordance with the temperature of the oil stored in the oil pan apparatus. More specifically, the open/close valve closes the communication paths when the oil temperature is lower than a predetermined temperature, and opens the communication paths when the oil temperature is not lower than the predetermined temperature, thereby permitting the passage of oil in the communication paths.
When the above conventional technology is used, the open/close valve closes at engine startup or in other situations where the oil temperature is low. Then, only the oil in the first chamber is supplied to the lubrication target mechanism and circulated between the lubrication target mechanism and oil pan apparatus. This increases the speed of oil temperature rise in the first chamber so that a warm-up operation may terminate early. Further, the open/close valve opens when the oil temperature is high. The oil stored in the oil pan apparatus is then entirely supplied to the lubrication target mechanism and circulated between the lubrication target mechanism and oil pan apparatus. This ensures that lubrication and cooling operations are properly performed for the lubrication target mechanism, and prevents the oil durability from deteriorating.